The present invention relates to a color filter substrate for a thin film transistor liquid crystal display (TFT LCD) and a manufacturing method thereof.
TFT LCDs, which have advantages of low power consumption, low manufacturing cost and substantially no radiation, have become mainstream in the current flat panel display market. A TFT LCD makes use of dielectric anisotropy and conductive anisotropy of liquid crystal molecules to display an image. Alignment of liquid crystal molecules can be modified when an external electric field is applied, causing liquid crystal material to generate various photoelectric effects.
A TFT LCD panel is formed by assembling a color filter substrate and a TFT array substrate facing each other. The color filter substrate and the TFT array substrate are separated with spacers to form a space for injecting liquid crystal material and are sealed with sealant to complete assembling of the display panel. The distance between the color filter substrate and the array substrate or a cell gap is maintained at a predetermined value. Typically, post spacers (PS) are prepared on the color filter substrate to maintain the cell gap between the substrates.
FIG. 1a is a cross-sectional view illustrating a conventional color filter substrate, comprising a glass substrate 101, a black matrix 102, color resin 103, and common electrode 104 disposed on the substrate 101 sequentially, with a post spacer 105 disposed on the common electrode 104.
FIG. 1b is a cross-sectional view for a pixel unit on the conventional color filter substrate. The black matrix 102 is provided for defining a pixel unit. Three neighboring red (R), green (G), and blue (B) pixel units comprise R, G, and B color resins 103 respectively. The common electrode 104 is formed on the black matrix and the color resins.
A conventional process for manufacturing a color filter substrate is described as follows. First, a black matrix 102 is formed on a glass substrate 101, followed by forming color resins 103 within the black matrix 102 on the glass substrate 101. Then a common electrode 104 is formed on the black matrix 102 and color resins 103. Lastly, a post spacer 105 is formed on the common electrode 104.
Since the post spacer 105 is positioned on the color filter substrate, the height of the post spacer is limited by the narrow cell gap. Even when a post spacer is formed of an elastic material, it is usually difficult to obtain sufficient elastic restoring force. In this case, if an external press goes beyond the predetermined elastic deformation range of the post spacer, a non-recoverable deformation is generated, leading to a cell gap variation. This variation may negatively influence the display and thereby affect the display quality of the liquid crystal display panel. Meantime, since the post spacer is positioned on the color filter substrate, the stability is poor. When subject to a horizontal impact, the post spacer may shift from its initial location, leading to light leakage.